i) Field of the Invention
The present invention relates to a paper separation mechanism for separating and feeding a plurality of sheets of paper stored in a paper storage sheet by sheet by cooperating with a paper feed mechanism having a feed roller, and to a paper feed apparatus having the paper separation mechanism.
ii) Description of the Prior Art
In a conventional paper feed apparatus as shown in FIGS. 16A and 16B, for example, a paper separation unit 92 is disposed such that the lower end surface of paper 90 abuts the paper separation unit 92. Friction between the paper separation unit 92 and the lower end surface of the paper 90 causes only the uppermost sheet of paper to be separated (cf. Publication of Unexamined Japanese Patent Application No. 2002-137838).
In the conventional paper feed apparatus, a separation unit retainer 93 retains the paper separation unit 92 by two retaining portions 93a and 93b protruding upwardly and being arranged along the longitudinal direction of the separation unit retainer 93. A clearance 93c is formed between the paper separation unit 92 and the separation unit retainer 93 so as to provide flexibility to the paper separation unit 92.
The paper separation unit 92 made of rubber material such as polyurethane has a convex end surface configuration that corresponds approximately to the end surface configuration of a holder 91 disposed over the paper separation unit 92. As shown in FIGS. 17A to 17C, the paper separation unit 92 is provided with a protruding portion 92a, which is designed to always protrude from through an elongated hole formed in the metal holder 91 so as to extend in the stacking direction of paper. The height of the protruding portion 92a is such that a predetermined amount protrudes from through the elongated hole of the holder 91. The lower ends of the plurality of sheets of paper 90 stored in a paper storage abut the upper surface of the protruding portion 92a. 
The upper surface of the protruding portion 92a is provided with small concavities and convexities 92b. The small concavities and convexities 92b is designed to increase the friction to occur between the lower ends of the plurality of sheets of paper 90 and the protruding portion 92a. 
In the conventional apparatus, as described above, the paper 90 is separated sheet by sheet by the friction of rubber material and an operation to increase the friction by the small concavities and convexities 92b, based on the balance with the feeding power of a feed roller.
In the above conventional apparatus, however, the load of the paper is carried by the entire protruding portion of the paper separation unit. This results in a problem that determination of the bending of the paper separation unit as well as design and manufacturing of the small concavities and convexities to be provided on the protruding portion are complicated, since the load imposed on the protruding portion changes substantially depending on the number of sheets of paper providing the load on the paper separation unit.
There is also another problem that the amount of protrusion of the protruding portion 92a of the paper separation unit 92 from the holder 91, which is determined depending on the elasticity of the paper separation unit 92 made of rubber material, constantly changes depending on conditions such as temperature and humidity, and is therefore highly unstable.
The present invention has been made in view of these problems, and it is an object thereof to provide a paper separation mechanism that assures sheet-by-sheet feeding of paper by preventing feeding of a plurality of sheets of paper simultaneously and requires no complicated design or manufacturing, as well as a paper feed apparatus using such a paper separation mechanism.